1. Field of the Invention
The present invention relates to liquid injection and atomization, and more particularly to multi-point fuel injection such as in gas turbine engines.
2. Description of Related Art
A variety of devices are known for injecting or spraying liquids, and for atomizing liquids into sprays of fine droplets, such as for gas turbine engines. Pre-filming air-blast fuel injector nozzles for issuing atomized fuel into the combustor of a gas turbine engine are well known in the art. In this type of nozzle, fuel is spread out into a thin continuous sheet and then subjected to the atomizing action of high-speed air. More particularly, atomizing air flows through concentric air swirl passages that generate two separate swirling airflows at the nozzle exit. At the same time, fuel flows through a plurality of circumferentially disposed tangential ports and then onto a pre-filming surface where it spreads out into a thin uniform sheet before being discharged from the edge of the pre-filming surface into the cross-flowing air stream.
Because the cross-flowing air stream has a much higher kinetic energy it excites the lower kinetic energy fuel sheet. That interaction serves to shear and accelerate the fuel sheet, creating multiple modes of instability, which ultimately results in the fuel sheet breaking into ligaments of fuel. These fuel ligaments are similarly excited and broken into droplets. This is the primary mode of droplet formation, requiring that the cross-flowing air stream has sufficient energy to cause excitation.
Improvements in spray patternation have been made by recent developments in multi-point injection, in which a single injector can include multiple individual injection orifices. Exemplary advances in multi-point injection are described in commonly assigned U.S. Patent Application Publications No. 2011/0031333 and 2012/0292408. These designs employ swirl features formed or machined in injector components to generate swirl in flows of liquid and/or air issuing from each injection point.
Such methods and systems have generally been considered satisfactory for their intended purpose. However, there is an ongoing need in the art for further improvements in injection, such as improved filming characteristics, improved discharge coefficients, improved hydraulic cone angles, and the like. There also remains a need in the art for such improved systems and methods that are easy to make and use. The present invention provides a solution for these problems.